1. Field of the Invention
The present invention relates to a fuel supply control method of an internal combustion engine used in a motor vehicle or the like, and more particularly to a fuel supply control method and apparatus which executes a control for increasing an amount of fuel in a transient state such as an accelerating time or the like.
2. Description of the Related Art
In conventional, in the case of supplying the fuel to the internal combustion engine by using an injection apparatus, an improvement of a power performance of an internal combustion engine, an exhaust gas purification, an improvement of a fuel consumption, an improvement of a drivability and the like are intended by controlling an injection amount of the fuel from the injection apparatus by an electronic control unit (ECU) so as to set a rate with a concentration of an air-fuel mixture between a fuel and a fuel supplied into a cylinder (a so-called an air-fuel ratio) to a predetermined value.
Further, the injection amount of the fuel can be theoretically calculated, however, since a preferable injection amount does not coincide with a theoretical value in some operating condition in an actual internal combustion engine, an appropriate control is executed by detecting actual measurement values from various sensors placed at necessary positions so as to compensate the theoretical value.
Further, in the fuel supply control method, a compensation control is necessary due to a displacement between a timing for detecting a throttle valve opening degree and a time required for computing a target injection time. As one of the compensation controls, for example, there is generally executed a fuel supply control method of increasing an amount of the fuel in a transient state such as an accelerating time or the like so as to increase an output of the internal combustion engine, which is proposed, for example, in Japanese Patent Publication No. 63-8296, Japanese Unexamined Patent Publication No. 3-43640, Japanese Unexamined Patent Publication No. 6-272601, Japanese Unexamined Patent Publication No. 2002-4992 and the like.
However, when executing the fuel amount increasing control which has been conventionally known, for example, in the case that a distance between an injection apparatus supplying the fuel and a combustion chamber of the internal combustion engine is long, a time lag with respect to a response from a detection of an acceleration state to the fuel amount increase is large. Accordingly, if a deceleration is executed just after an acceleration (hereinafter, refer to as “acceleration and deceleration operation”), the fuel enters into the combustion chamber more than necessary, in particular, if the acceleration operation is continuously executed for a short time, there is generated a phenomenon that the air fuel ratio becomes rich, so that there is generated troubles such as a black smoke generation from an exhaust pipe, an engine stop and the like.
Further, Japanese Unexamined Patent Publication No. 9-203335 proposes a fuel amount increase control means for preventing the air fuel ratio from becoming rich by storing a matter that a fuel amount increase control is executed at a time of an acceleration operation in an electronic control unit, thereafter not deleting the memory until a throttle valve opening degree is returned to a predetermined low position, and inhibiting the fuel amount increase control even if the throttle valve opening degree becomes in a transient state due to the acceleration until returning to the predetermined low position.
However, in the fuel amount increase control means proposed in Japanese Unexamined Patent Publication No. 9-203335, the fuel amount increase control is executed at a time when the throttle valve is opened at the accelerating time, and it is unavoidable that the fuel enters into the combustion chamber more than necessary if the acceleration and deceleration operation is executed in the case that the distance between the injection valve supplying the fuel and the combustion chamber is long.
Further, since the throttle valve opening degree is returned to the predetermined low position, whereby the memory is deleted and the inhibition of the fuel amount increase is cancelled, the fuel amount increase is continuously executed in the case that the acceleration and deceleration operation is repeated at two or more times for a short period.